Railway traffic controlling apparatus



' y 8 9 A H. 1A; THOMPSON 2,401,201 RAILWAY TRAFFIC CONTROLLiNG APPARATUS I Filed July 31, 1942 4 Sheets-Sheet 1 May 28, 1946.

H. A. THOMPSON RAILWAY TRAFFIC CONTROLLING APPARATUS Fild July 51,1942 4 Sheets-Sheet 2 j fastball/2d n m M A a a May 28, 1946; THOMPSON 2,401,201

RAILWAY TRAFFIG CONTROLLING APPARATUS I Filgd July 31-, 1942 4 Sheets-Sheet 4 fy/d .v

955.. l 111m 1770mm? Patented May 28, 1946 The Union Switch & si a obfii aflyfs s val e,"Pa., a corporation Application mm; 13 Claimsif My invention relatesto railway traflic .controllingapparatus, and has particular referencei to novel and improved forms of. railway traflic controlling systems of the absolute permissive block (A. P. B.) type arrangedv to .control the: movement of traific in either directionover-a stretch of single track railway. More particularly, my invention relates to AP. B. signa1. systerms of the class incorporating coded track circuits arranged to obviate the useinsuch systems.- of control linewires.

It has been proposed heretofore to'provide A. P. B. signal systems which incorporate coded track circuits arranged in such a manner as to render unnecessary the use of control line wires. ,One system of this type is disclosedin; Letters Patent: of the United States No. 2,280,491,,granted one April 21, 1942, to Ralph R.-Kemmerer. ThQSXSn tem of this patent employs two tracktcircuitsnfor a each track section, with the coded current; (mas,- ter code for one track circuit suppliedfrom one. end, and the coded current (feed back code); for the other track circuit supplied fromthe other end of the section, the second track circuit being dependent for its operationupon the supply of, code to the first track circuit from a suitable code, transmitter or coding device. 1, V v

It is aniobject of my present invention tolprovide a novel and improved A. l. 13. signal system i which also employs two track circuits per section, but which operate on the self-generatingjfcode principle disclosed in a copending application, Serial N 0. 443,240, filed on May 16, 1942 by lohn M. Pelikan. In accordance with this prii cipl ea the codings of the two track circuit energies ofna section are made mutually dependent and each. coded energy is generatedin response to the pres: Q ence of the other coded energy. v i

Another object of my invention is theprovision of a novel andimproved signal system incor porating coded track circuits which are arranged so that in normal operation coded energy is generated without requiringspecial devices, such as: code transmitters. a I

A further object is the provision of a novel and improved 'A. P. B. signal system in which traflic in either direction over a stretch'of track isc'orl j trolled by coded track circuit energy of the fcountj i code"type. I 1

An additional object is the provision. ofa' novell and improved form of signal system of th nw h use f l contro l n wi es: is made unnecessary by the employment of coded type track circuits. R a a i I";

Another objectis the provision,;in aisignal sysof Pennsylvania 1942, Serial 452,983- 59 -245 l temof-the' single trackgtwo direction type, "of

coded track' circuit current havinga plurality of code patterns one of which is employed solely to detect"the presence of *trafilcf and the others of which are employed to establish controlover traffic,fw.;..c;. i

A still furtherobject'is the provision of novel andimproved track circuits of the selfegenerat code'class l 1 Anotherobject is the organization of railway traffic:contro11ing apparatus into a'novel and improved form ofrailway signal system. q

:The. abovermentioned' la/S' W81L asv other .important objectss'andi characteristic 'featureslof my 151 invention: which will; become readily app fromithe .afollowingodescription, are attained in accordance with the invention. by organizing .into

amA'.aB. B.. .signal.systemaapparatus which providesx-eachgsection. of: trackwith two track circuits i one-.for each direction .or traffic on thefstretch. Each of these track circuits issupplied withcodede current; which current reflectstraflic. conditions inadvancefor theassociated direction of trafiic and whiohis generated in response to the presence of track circuit current in the othertrack circuit oftheisection.) Incorporated into the system are 1 means forrattaining absolute lopposing and permissive following protection .foritrains. on the stretch,

301 Other-features of thevinvention residein thl pa t cular app atusemplo d a dz n. the specific arran m ntof su h epparatus aswill be p nted .1

tin detail here ua te n the ec fic tiona id laim one r ern ir inten ion; sa dvshall h ir i t out th q el' fea uresthereoimpla m V and id, when placed side by side with Fig. 1a 40 on the. left, are a diagrammaticview illustrating apparatus and circuitscomprisinga portion of an absolute permissive block signal system em,

bodying my invention In each of the several u es. the dra n s, s mi ar r r n C ev ch itbhesl th succe s e P ssin d nss W and a 'r rrai si Q s iretchia l s iv ed rins td: Jo nt 21 into. .i

IV The reiierence characte s vw t sii filrdislama oi attests; em dy! nnected ;b y; track I ;n .1. ra i o u s ve-a i n natra k ec i ns I IL. II-17W a d.

by signals having even numbers in their respec tive prefixes, whiletrafiicoperating in the opposite or westbound direction is governed by signals having odd numbered prefixes. In accordance with the usual custom in A. P. B. signaling, signals trolled through the medium of the associated control relays in accordance with the usual A. P. B. practice by apparatus arranged to provide each track section with two track circuits, one for each direction of traffic. These track circuits are arranged to incorporate the self-generating code principle ofthe aforesaid Pelikan application Serial No. 443,240. In general, each section is provided with the following: two sources of track circuit energy, which sources may for example be track batteries designated by the reference .character 'TB with suitably distinguishing pre- 28 and 9S at the leaving ends of traflic sidings W and E, respectively, are absolute or stop and stay signals and will be termed headblock sig-" nals, while the other signals of'the stretch are permissive or stop then proceed" signals.

The signals S may be of any suitable type,-but 2 for the purpose of this application it will be assumed that the signals are of the color light type and that each comprises a plurality of lamps G, Y and R ,efiectivewhen ,i-lluminatedto display a clear, approach, or stop aspect, respectively. 'Each signal S has associated therewith a.

distant signal control relay D; a home-signal control relay H; and a detector controlrelay T1. The manner in which these relaysare controlled will be made clear presently but at this time it should be pointed out that the signalcontrol relays govern local circuits over which the associated signals are respectively controlled. Each signal is caused to. display its clear aspect when the associated distant, home and detector relays are picked up; is caused to-displayits approach aspect when the associated'distant relay D is released and itsassociatedhome H and detector'TP relays are picked up; and is caused to display its stop aspect whenits associated distant D and home H relays are released, irrespective of whether the associateddetectorrelay TP is picked up or released. Thus, for example, signal is at location I will: display its clear aspect. when its lamp G is energized over a circuit which may be traced from one terminal B of a suitable source of ener y, such as a battery not shown but having its terminals designated by the reference characters B and C, through front contact loo-r relay- ITP, front contact ll of'relay IH, front contact 12 of relay ID and the filament of lamp G of'signal IS to the other terminal C of the source of current; the signalwih display its approach aspect when lamp Yis energized overa circuit extending from terminal H through front contact IU of relay ITP, front contact [I of relay lH,

back contact l2 of relay I'D andthe'filament of lamp Y of signal IS to -temiinal-Cr andthesignal will display its stop aspect when lamp R is energized over a circuit which extends from terminal B either through front contact H!- of relay ITP and back contact H of relay l I-I or through back contact ll) of relay ITP, then through the filament of lamp R of signal lS toterminal C.

The signal control relays are provided with slow releasing features inany suitable manner. Relay ITP, as shown, may be made slow to release by connecting a resistor across its terminals, while relays Ill and 1-D may be made slow tdrel'ease,

as shown, by connecting asymmetrical units across their respective tenminals; Other expe fixes, one battery for each end of a section, respectively; two track relays, designated by the reference character TR with suitably distinguishing. prefixes, one relay for each end of a section; decoding means operatively associated with each track relay for detecting and translating the operation of the associated track relay in response to coded current received by the track relay from the rails of the section; and code generating means operatively associated with each track relay for generating coded energy which is applied to that end of the section for causing operation of the track relay at the opposite section end.

The track circuit apparatus. of each section is arranged so that the track relay at one end of a section is at times connected through the track rails in series with the track relay and source at the other or opposite section end, while at other times the track relay at said other section end is connected throughv the track rails in series with the track relay and source at the said one section end.

To effectuate this arrangment, each track relay has associated therewith a code repeater relay, designated by the reference character CP with a suitable distinguishing prefix, arranged when picked up to connect the associated track relay TR and source TB in series with the track rails and effective when released to connect only the track relay TR but not the associated source TB to the rails. Code repeater relay 'ZCP associated with relay ZTR of section 1-11, for example, when picked up establishes a circuit connection which extends from rail la of section III, through the winding of relay 2TB, front contact l5 of relay 2GP, and the battery 2TB tothe other rail I of the section. When relay 2GP is released, the-winding of the associated track relay 2TB is connected across the rails l and la over an obvious circuit which includes back contact l5 of relay 2GP. The other track relay 3TH and battery 3TB of section II-I are similarly connectedto'rails-l and l d of the section by the associated code repeater relay 3GP, hence it follows that when code repeater relay 3GP is picked up and relay ZCP is released, both track relays ZTR and 3TR will be connected in series with battery 3TB through the track rails, and when relay ZCP' is picked up and relay 30? is released, both relays Z'IR and 3TB will be connected in series with the other battery 2TB- through the track rails.

The track batteries TB of a given section are poled in such a manner that the rail current flows in opposite directions in the two track circuits of "the section, and the two track relays of such section are of the biased polar neutral type that will respond to current of but one relative accuser viewed intheidrawings and. indicates thatxthe relay will respond to current of the polarity that will ,make'the left-hand termina1fof-therelay positive. The track relays and track batteries are so arranged that each track relay will be nonresponsive to current supplied from the associatedsource at the same end of the section but willv respond to current supplied from the source at the opposite sectionend. Relay 2TB will thus be picked up by energy supplied from battery 3TB but not from. battery 2TB, whereas relay 3TH. will be picked up by current supplied from battery. 2TB but not from battery 3TB. p

The code generating. means associated with each track relaycomprises a plurality of impulse relays, designated by. the reference characters N, P- and Q, each with a suitably distinguishing prefix; a plurality of stick relays, designated bythe reference characters NS and ,PS, each with a suitably distinguishing prefix; and in .addition one .track=.relay of each sectionhas associated therewith codeinitiating or resetting means comprising two auxiliary relays FC. andBC provided for the associated detector control relay TP. The auxiliary relay BC and each impulse relay 'N P and Q is effective when picked up. to energize and pick up the associated code repeater relay CP, thereby to causethat repeater relay to conmeet. its associated source TB to the track rails and apply an impulse of energy to such rails. The impulse relays N, P and Q are controlled, as will be made clear presently, in such a manner as to cause the energy impulses applied to a track circuit to reflect traflic conditions in advance for the direction of traffic governed by such track circuit. This control of the impulse track'current is accomplished by supplying to a track circuit one or another of aplurality of codes of the count code type: These codes are each comprised of impulses of energy that are supplied-in re-' current groups of one, two, three, or more impulses per group. a The impulses preferably are of approximately equal length and are separated from oneanother by relatively short .off periods, while the. groups of impulses are separated from each other by an off or open circuit interval of relatively longer duration. l

The apparatus represented in the drawings embodying the present invention is arranged to employthree .difierent codes of the count code type, but it is to be understood, of'course, that a larger or smaller number of such codes maybe employed if conditions warrant. One of the three codes employed comprises recurrent groups of three energy impulses a second code comprises recurrent groups of two impulses; while the third code comprises successive single energy impulses The first .two codes are employed, as willbe described in detail hereinafter, to indicate orrefle'ct clear and caution traffic conditions, respectively, while the third code is employed solely as a detector code and its presence reflects an unoccupied condition of the track. i

= The decoding means associated with each track relay comprises a track stick relay, designated by the reference'character TS with a suitably distinguishing prefix; a decoding transformer, designatedby the reference characterDT with a suitably distinguishing prefix; a plurality of impulse counting relays, designatedby the reference charactersJ, K, L and M, respectiv l each with a suitably distinguishing prefix; and the, distant, home and detector control relaysD, H andTP, hereinbefore mentioned. These control relays are, governed by the; associated trackstick and relay D. associated therewith are all picked up and as a; result the: associated signal-is conditionedst display its-clear aspect. The particular arrangement. of this apparatus and the mannerpof its operationswill be given in the description whichfollows. Y H ,,-The;reference characters SR with suitably distinguishingrprefixeswdeslgnate the usual direce tional stickrelayswhich are-provided in pairs at each signal lccation-s'other than at a headblock location. -.These stick: relaysfunction to establish directional control ;of.traffic on the stretch in a mannerthatwill be made clear presently.

'The system organization may also include cutsectionlapparatus. which is. effective to repeat or cascade code energy from one section to the next. A suitable formof su'chapparatus is represented in Fig. 10 at the cut-section location III. This apparatus comprises two track batteries TB and twptrack. relays TR one for each section and each connected across the:rails of theiassociated section. through .acurrent limitingtresistor l8. Each cut-sectiontrack relay when released completes through:its "back contact IS an obvious shunt circuit, around the current limiting resistor l 81 of the other put-section track relay, and each of these, track relayswhen picked up opens the shunt gcircuitd and connects. its associated track multiple withthe series combination of the winding of. the other cut-section track battery and the associated resistor 18. .Itis thus readily apparent that each time a cut-section relay is picked up by a code impulse of energyof the proper polarity received.fromltherails of its associated section, the battery associated with such cut-section relay is then connected to the rails of the adjoining section to impress thereon an impulse of energy. Each cut-section vtrack relay'is thus capable of repeating or cascading track circuit code energy from its associatedsection into the next adjacent sectionp The track circuit apparatus embodying my invention is arranged,-asfstated hereinbe fore, to reflect traflic conditions in advance by applying to'the rails of each of the sections track circuit energycoded in one or another "of a plurality of different manners each indicative of different I--II, arranged and operating in the following manner. I

Referring to the drawings, the track circuit apparatus provided at section end I of section 1-11 is illustrated in Fig. 1a in the condition that is established following the receipt of the last impulse of a group supplied from Source 3TB at the opposite section end II, and in which condition-the apparatus at sectionend I is arranged to start the transmission of track circuit code energy to the other end of the section. In this condition of the apparatus, track stick relay ZTS is held energized over a stick circuit that extends from terminal'B through back contact 24 ofrelay 2N, front contact 23, and the winding of relay ZTS to terminal C; relays 2TP, 2H and 2D are deenergized but are represented in their pickedup positions wherein they are held by their slow releasing characteristics, with the result that lamp G of signal 28 is energized over its previously traced circuit; and all other relays at location I associated with section III .are released. With relay released, battery 2TB isdisconnected from the rails, track relay ZTR is connected across the track rails of the section, and relay 2N is energized over a circuit extending from terminal B through back contact 2| of'relay ZTR, front contact 29 of relay 2T5, and the winding of relay 2N to terminal C. Relay 2N is so proportioned as to have a predetermined slowpick-up interval and will pick up at the end of such interval, but at this time it is assumed that the relay is released.

Considering now the apparatus at the opposite end II of the section, this apparatus is illustrated in Fig. 1b in the condition that exists following the supply of the last impulse of a group from track battery 3TB to the rails of section III, and in which condition the apparatus is arranged to receive energy from the track rails; Under such assumed conditions, relays 3TP, 3H and 3D are deenergized but are represented in their picked-up positions wherein they are respectively held by their slow releasing characteristics with theresult that lamp G of signal 38' is energized over an easily traced circuit; and all other relays at location II associated with section 1-11 are released. Since relay 3GP is released, track relay 3TB is connected to the track rails but battery 3TB is disconnected therefrom. At this time, therefore, both track relays 2TB and 3TB of section 1-11 are connected in series through the section rails, but no energy source is impressed on the rails hence the relays ar both released. This condition is maintained until relay 2N at location I picks up to initiate the transmission of energy from battery 2TB.

In describin the operation of the apparatus of section III, I shall first describe in detail the manner in which the code generating apparatus at section end I functions to transmit energy to the track rails, and shall then describe how the decoding apparatus at the opposite section end II detect and translates such energy.

Referring again to the apparatus represented at location I in Fig. 10; associated with section I--II, relay 2N picks up, at the endof its predetermined slow pick-up interval, to close its front contact 50 and to open the back point of contact 24 and to close the front point of this contact. When the back point of contact 24 opens, it interrupts the previouslytraced stick circuit of relay ZTS, whereupon that relay releases and operates its contact member fromilits front to its back point to reverseithe direction in which unidirectional current is supplied overan obvious circuit to Winding 25 of transformer ZDT. This results in a reversal of flux direction in the transformer and in the induction of an electromotive force in winding 21 which is impressed across relay 2T? over a circuit that extends from one terminal of winding 21 through back contact 28 of relay Z'IS and the winding of relay 2T1? to a mid-tap of winding 21. This energy impulse applied to relay ZTP energizes the relay and operates to hold up the relay for its predetermined slow-release interval.

In addition, the release of relay 2T8 results in the opening of its stick circuit at its front contact 23, and in the opening of the previously traced energizing circuit of relay 2N at front contact 29. Relay 2N accordingly becomes deenergized but its front contacts 5.0 and 24 remain closed long enough (following the brief energization of relay 2N).to enable relays 2CP and ZNS to bepicked up, in the following manner. Relay 2GP is picked up over an obvious circuit which includes front contact of relay 2N, and relay 2GP in turn closes its front contact [5 to connect battery 2TB to the rails of section 1-11 in series with the winding of relay 2TR. The current supplied from battery 2TB has a polarity such that it does not cause relay ZTR to pick up but is effective to pick up relay 3TR at the opposite section end, but since the opera- ,tion of relay 3TB by this energy will be de scribed hereinafter in connection with the description of the operation of the apparatus at section end II, no further .description of the operation of relay 3TB, will be given at this time. Relay ENS also becomes energized at this time, over a circuit which may be traced from terminal B through front contact 24 of relay 2N, and the winding ofrelay 2N8 to terminal C. This relay picks up. and closes its front contact 53 to complete a stick circuit that extends from terminal B through back contact 54 of relay 2P,'front contact 53 and the winding of relay ENS, to terminal C. Front contact 55 of relay 'ZNS also closes and relay 2P becomes energized over n obvious circuit including this contact. Relay IP is slow to pick up and will pick up at the end of a predetermined time interval which is considerably shorter in duration than the pick-up interval of relay EN. The slow pick-up interval of relay 2P may be, for example, only a little longer than the time required for relay 2N to release.

After relays 2GP and ZNS have picked up, relay 2N releases and' as a result relay 2GP is deenergized and in turnreleases to disconnect battery'QTB from the track rails. This terminates the first impulse of energy of the group that is transmitted from battery 2TB to the rails. Relay 2NS does not release since it is held energized over its previously traced stick circuit, hence the energizing circuit of relay 2P is maintained closed and that relay picks up at the end of its slow pickup interval. When relay 2P picks up, its back contact 54 opens and interrupts the stick circuit for rela 2NS to deenergize this relay, thus causing the energizing circuit of relay 2P to be interrupted at front contact '55. Relay 2P accordingly becomes deel'iergized but holds its front contacts 54 and 5'! closed for an interval sufficient to enable relays 2CP and ZPS to pick up. Relay 2CP picks up over anobvious circuit including front contact 51 of relay 2P, and again closes its front contact 15 to connect battery 2TB to the rails in series with relay 2TB, thereby to initiate the transmission of the second impulse of energy throughthe track rails. Relay 2PS picks up over a circuit extending from terminal .B through front contact 54 of relay 2P, the winding of relay 2P5, andfront contact 65 of relay ID,'to terminal C. It is to be seen that when rela ID (which detects the three pulse clear code energy in its associated section in a manner substantially corresponding to that hereinafter described in detail in connection with rela 3D of section I--II) is released, then relay 2PS cannot be energized and as a result the Coding action of the apparatus at location I and associated with section I-II will then terminate at the end of the second impulse supplied to the track rails. With lelay ID picked up, however, relay 2PS maybe energized and it picks up to close its front contact 56 and complete a stick circuit which passes from terminal B 'through 'back contact 59 of relay 2Q, front contact 58 and the winding of relay ZPS; and front contact 65 of relay ID, to terminal C. Front contact 60 of relay ZPS also closes and it completesan energizing circuit for relay 2Q that extends from tcrminal B through front contact 60 of relay ZPS, the winding of relay 2Q, and front contact 65 of relay ID to terminal C. Relay 2Q is slow to pick up and does not do so until hortly after relay 2Preleases. I [After relays ZCP and ZPS pick up, relay 2P releases and as a result relay'ZCP releases to disconnect battery 2TB from the track rails. This terminates the second impulse of energ of the group that is transmitted from battery 2TB. Relay ZPS remains energized, however, over its stick circuit until relay 2Q picks up at the end of its slow pick-up period. When relayZQ picks up, its back contact 59 opens to deenergize relay 2P5, which relay in turn releases and opens its stick circuit and the previously traced energizing circuit ofrelay 2Q. Relay 2Q holds its front contact 62'closed, however, for an interval sufiicient to energize relay 20? and 'causethat relay'to close its front contact I5 to again connect battery 2TB to the section rails in series with relay 2TR', thereby initiating. the transmission of the third impulse of energy to the rails. Rela 2Q releases shortly after relay ZCP picks up, and relay 2GP accordingly releases to disconnect battery 2TB from the track rails and thus terminate the third impulse of energy that is supplied to the track'rails. The apparatus at section end I of section I-II now is'in the condition wherein all relays are released except'relays ZTP, 2H and 2D, hence the apparatus is conditioned to receive track circuit energy from the rails of the section.

From the foregoing descriptiomit is readily apparent that the code generating apparatus provided at end I of section III is arranged to apply an'energy impulse to the associated track rails each time one of the impulse relays 2N, 2P and 2Q, picks up; and that each impulse relay is picked up over afront contact cf'a stick relay held energized over a stick circuit that includes a back contact of the impulse'relay. Each impulse relay accordingly interrupts its own circuit when it picks up. The first impulse relay (2N) picks up over a back contact of the track relay and requires that contact to be closed for a pre determined interval of time; and each impulse r'elay except the last impulse relay 2Q) picks up the stick relay controlling the succeeding impulse relay. It follows that additional codeimpulses may be provided, if desired; merel by adding additional stick-and impulse relays arranged in the manner described. r

1 The code generating apparatus provided at eac of the locations represented in the drawings is all arranged to'incorporate the features just described and hence each of such arrangements will function, in general, in the manner just stated. Inaddition, the arrangement of the apparatus represented at headblock signal locations I and V associated with sections I-II and IVV, respectively, is further characterized by the fact that the third impulse relay (Q) is controlled overa. front contact of the distant control relay (D) of the next adjacent section, hence clear or three pulse track'circuit code will be applied to the rails of the associated section when relay D of the next adjacent section is picked up, but whenthat relay is released the track circuit code is then shifted to the caution or two pulse pattern. I

The specific arrangement of the code generating apparatus located at the headblock signal locations I and V and'associated with the sections that extend respectively to the west of location I and to the east of location V, is characterizedmy the fact. that the second impulse relay Pand its associated stick relay NS are controlled over a front contact 68 of the detector control relay (TP) of the next adjacent section, while the third impulse relay Q and its associated stick relay PS are energized over a front contact 6| of the home control relay (H) of the next adjacent section. Thus, for example, relay INS at location I is energizedover a circuit that extends from terminal B through front contact 24 of relay IN, thewinding of relay INS, and front contact 68 of relay ZTP to terminal C; relay IP is energized over a circuit that may be traced from terminal B through front contact 55 of relay INS, the winding of relay IP, and front contact 68 of relay TI? to terminal 0; relay I PSis energized over a circuit passing from terminal B through front contact 54 of relay IP, thewinding of relay IPS, and front contact SI of relay 2H to terminal C and relay IQ is energized over a circuit extending from terminal B through front contact 60 of relay IPS, the winding of 'relay IQ, and front contact 6| of relay 2H totermlnal C, It follows, therefore, that when relays HP and 2H are picked up, the code generating apparatus at location I is conditioned to apply clear or three pulse code energy to the section that extends to the west-of location-I;.when relay 2TP'is picked up. but relay 2H is released, then the code supplied to that section is shifted to the two pulse caution pattern; and when relays TI? and 2H are both released, then the code energy supplied to the section comprises the one ulse detector code.

The specific arrangement of the code generating apparatus located at, the intermediate signal locations II and IV, is characterized by the fact that the second'impulse relay Pand its associated'stick relay NS arecontrolled over a front contactil of the home control relay H of the next adjacentsection, or alternately over a back contact of that H relay and a front contact 52 of the directional stick relay SR associated with such next adjacent section; while the third impulse relay Q and its associated. stick relay P3 are controlled over a front contact SI of the home control relay H of the next adjacent section. For example; the energizing circuit of relay 3NS at location II'extends from terminal -B through front contact 24 of relay 3N, the winding of relay 3N8, and the front pointof contact 5I'of relay 4H, or alternately through the back point of contact SI and: front contact 52 of relay 48R.

to terminal C;-relay SP :is energized over afci'rcuit extending fi'omaerminal'B through from contact 53 of relay 3NS,-th'e winding of :relay 3P, and the front point of contact 5| of relay 4H, or the back point of 'contactii and front'contact 32 of relay 38R, to terminal'Cywhile'the energizing circuits of relays 3PS- and 3Q'aresimilar, respectively, to the circuits previously traced for relays IPS and IQ. It is apparent, therefore, that when relay 4H is picked up, three pulse clear code energy will'be applied at'locationII to section I-II; when relay 4H is released and relay QSR is picked upgtwo pulse caution code energy will be applied at location II to this section; and when relays 4H and lSR are both released, then one pulse detector code energy will be applied at location 11 to the rails of this section. I Thearrangement of controls of the clear and caution c'odesjust described is that usually employed in A. 1?. Bj'signalingk It will lac-obvious, however, that the control of clear and caution codes may readily be altered to accommodate various arrangements of A.- P. B. control limits as required by any particular arrangement "of track and sidings. Y I

I shall now describe indetail how the decoding means at location II associated withsection I-II functions to detectand translate the coded energy that is applied at the'opposite section end I by the code generating apparatus thuslo'cated; Referring now to the'apparatus represented at location II, that apparatus remains in the conditionillustrated o-aaynreyan, and 3Dpicked up but deenerg'ized and all otl'ier relays released) until th'e first impulse of energ'y'isapplie'dfroni battery 2TB to the rails" ofseCtion'I-II at its opposite end I. When this happens, the energy impulse is transmitted through the track rails ofthe sectionto relay-3TR'and since it is of the properpolarity to'operate' relay 3TR, th'at relay picks up and closes its front contact 2|, where"- upon track stick relay 3T8 picks up over'a circuit thatexte'nds from termina-I'B 'thrdugh from contact 2 I of relay 3"1R,-back Contact 22 of relay SJ and the winding of relay '3TS, to terminaro. Relay 3TS closes its front contact 23 and'completes a stick circuit that extends from terminal B through-back contact 24 of relay 3N, front contact 23, and'the windingof relay' 3TS to terminal C. This'stick circuit obviously is'effective to maintain relay 3T8 picked"up until relay 3N is caused to pick up'and open its back contact 24. v

Relay 3TS also operates its contact 2 5 from its back to its front point and thereby reverses the direction in which unidirectional current is supplied over an obvious'circuit to primaryiwinding 26 of transformer 3DT. This, in turng 'rev'erses the direction of the flux in th'e transforn'ier and causes an electrom'otive force to be induced in secondary Winding 21, which induced energyimpulse is supplied'torelay3TP' over acircuitthat extendsfromene terminal of windin'gil through front contact 28 of'relay 3TS;'the winding of relay 3'IP and to the rnid-tap' 'o'f-vvindi'ng 21. This energy impulse'energizes relay 3T-P'and is effective to holdup the relay for its predetermined slow release interval; At the end or the first'tra'ck fenergy impulse,

relay 3TB releases-and closes its back contact 33 to pickup relay 3.] over a circuit that may be traced from terminal B-through back 'contact'30 of relay 3TB, frontcontact 3i ofrelay 3T8, the winding of relay 3J, back contact32 of relay 3K, back contact 33 of relay 3L,ba'ck contact'ile of picks up, it closes its front contact 31 and completes a stick circuit for itself that extends from terminalB through back contact 36 of relay 3K,

front contact 3'! and the winding of relay 3J, and back contacts 32, 33, 34 and 35 of relays 3K, 3L, 3M, and 3N, respectively, to terminal C.

Relay 3TR in releasing also closes-its back contact 2|. and relay 3N becomes energized over a circuit extending from terminal B through back contact 2i of relay 3TB, front contact 29 of relay 3'IS and the winding of relay 3N to terminal C. Relay 3N is slow to pick upandis proportioned to have :a'pick-up interval such that the relay willnot pick-up'unless relay 3TR is released for an interval-greater than the interval between successive impulses of a group. If, therefore, the energyappliedto' the trackrails is of the single pulsedetector type, then relay 3N would pick up at the end of its predetermined pick-up interval following each release of'track relay 3TR at the end of each of the single impulses which comprise that type of code. Under such assumed conditions, only detector control relay 3T? would be energized by the operation of relays 3TB and 3TS--inresponse to the coded energy, and relays 3H and 3D would be deenergized to cause the associated signal to display its stop aspect. The energization of relay 3TP accordingly is effective to detect the single pulse detector code energy.

'When, however, the energy in the track rails is of the type (as has been assumed) that is comprisedefmore than a single pulse in each group, then relay 3TB will pick up in response to the second impulse of the group, prior to relay 3N picking up'l When relay 3TB; picks up, its back contact 2! opens to deenergize relay 3N, and its front contact 33 closes to energize relay 3K over a circuit'that passes from terminal B through front contact 33 of relay 3TB, front contact 38 of relay' 3J'(which relay is now held energized over its stick circuit), the Winding of relay 3K, and back contacts 33, 34 and 35 of relays 3L, 3M and 3N, respectively, to terminal C. Relay 3K accordingly picks up and closes its front contact M'to complete a stick circuit that extends from terminal 13 through back contact 39 of relay 3L, front contact 30 and the winding of relay 3K. and back contacts 33, 34 and 35 of relays 3L, 3M and 3N, respectively, to terminal (3'. Relay 3K also opens its back contacts 32 and 36 to open the previously traced stick circuit of relay 3J, which relay is slightly slow to release and holds itsfront'contact M closed for an interval during Which-relay 3H becomes energized over a circuit extending from terminal B through front contact 36 of relay 3K, front contact 4| of relay 3J, the winding'of relay 3H, front contact 42 of relay 3TP, and back contact 43 of relay iSR to terminal C. This energy is effective to maintain relay 3H in its picked-up position for its predetermined slow release interval after relay 3J releases.

"At the end of the second energy impulse received from the section rails, relay 3TR releases and closes its back contact 30 to complete a circuit that extends from terminal B through back contact 33' of relay 3'IR, front contact 3| of relay 3T8, front contact 44 of relay 3K, the winding of relay 3L, and back contacts 34 and 35 of relays 3M and 3N, respectively, to terminal 0, whereupon relay 3L picks up and closes its front contact 46 to complete a stick circuit that extends from terminal B through back contact 45 of relay 3M, front contact 46 and the winding of relay 3L, and back contacts 34 and 35 of relays 3M and 3N, respectively, to terminal C. Relay 3L also opens its back contacts 33 and 39 whereupon relay 3K becomes deenergized and releases to interrupt the energization of relay 3H.

At this time, relay 3N is energized over its previously traced circuit including back contact 2! of relay 3TB, but due to its slow pick-up characteristics, relay 3N does not pick up immediately and will not do so unless rela 3'I'R remains released, as stated hereinbefore, for an interval greater than the intervals between successive impulses of a group. Thus, for example, should the energy in the track rails be of the two pulse caution type, then relay 3N would pick up at the end of its predetermined pick-upinterval following eachrelease of track relay 3TB at the end of each of the second impulses of the groups which comprise the caution code type of energy. In such an event, the detector control relay 3TP and home control relay 3H would be intermittently energized by the operation of relays 3TB, STS, 3.] and 3K effected by such two pulse coded energy, but relay, 3D would be continuously deenergized and would be released with the result that signal 38 would be caused to display its caution aspect, In addition, it is to be noted that relay 3H is controlled over a back contact 43 of stick relay 48R associated with the next adjacent section 11-111, hence it follows that if relay 4SRis picked up, relay 3H cannot be energized and under such conditions signal 38 would be caused todisplay its stop aspect even though caution or clear code energy might be available in section I-II, for operating relay 3TH.

When, however, the code energy in the track rails is of the three pulse clear code type (as has been assumed), then relay 3TB is caused to p ck up in response to the third impulse of the group, prior to relay 3N picking up, When relay 3'I'R picks up, relay 3N is deenergized and relay 3M picks up over a circuit that may be traced from terminal B through front contact 30 of relay 3TR, front contact 41 of rela 3L, the winding of relay 3M and back contact 35 of rela 3N to terminal 0. When relay 3M picks up, it opens its back contacts 45 and 34 to deenergize relay 3L, and relay 3M also closes its front contact 4-5 to energize relay 3D over a circuit that extends from termina1 B through front contact 45 of relay 3M,

the winding of relay 3D, front contact 48 of relay 3H, front contact 42 of relay 3TP and back contact 43 of relay 48R to terminal C. It is to be noted that this circuit also includes a back contact 43 of stick relay 48R, thus requiring that relay to be released in order to enable relay 3D to be energized when the clear code energy is available in its associated section I-II to operate relay 3TB.

At the end of the third energy. impulse of a group, relays 3TR and 3M release, and energy is removed from relay 3D, which relay is then maintained in its pickedup position, due to its slow releasing characteristics, for its predetermined release interval. Relay 3N is now energized and will pick up at theend of its slow pick-up interval.

When relay 3N picks up, it will initiate the transmission of code energy from batter 3TB to the rails of section I-II, which coded energy will be generated by the code generating apparatus at location 11 in a manner that has been made clear hereinbefore. This coded energy will have the proper polarity to cause relay 2'IR to pick up, and the decoding means associated with relay 2TB will function to detect and translate such energy in a manner that substantially corresponds to the manner just described for the decoding apparatus at location II associated with relay 3TB.

From the foregoing description, it is readilyapparent that the decoding apparatus provided at location II associated with relay 3TB i arranged to pick up the track stick relay 3T6 and supply an energizing impulse to detector control relay 3TP whenever relay 3TB is picked up by the first energy impulse of a group received by the track relay; impulse counting relay 3K is picked up to supply an energizing impulse to home control relay H whenever track relay 3TB. i picked up by the second impulse of a group and relay 3J is picked up due to the release of relay 3'IR following the first energy impulse; and that impulse counting relay 3M is picked up to supply an energizing impulse to distant control relay 3D When ever track relay 3TB. is picked up by the third impulse of a group and relay 3L is picked'up due to the release of relay 3TR following the receipt of the second energy impulse of the group. It follows, therefore, that the first energy impulse of a group is detected by relay 3TP which is supplied with energy through the medium of the track stick relay 3T8 and decoding transformer 3DT; and each of the succeeding impulses of a group is detected by the control relays Hand D which are supplied with energy over circuits controlled by impulse counting relays arranged to be sequentially energized, with the first counting relay being energized over a contact of the track stick relay, a contact of the track relay and back contacts of each of the other counting relays; The succeeding impulse counting relays are each energized over a contact of the track relay, a front contact of the impulse counting relay that immediately precedes it in the chain, and back contacts of the counting relays that follow in the chain. It can be seen, therefore, that additional impulses of a group can readily be detected by providing additional counting relays, two for each of the additional impulses, and by arranging the relays in the manner just described.

The decoding apparatus provided at each of the locations represented in the drawings is all arranged to incorporate the features just described and such apparatus will function, in gen: eral, in the manner described in detail hereinbefore. Specifically, the decoding apparatus provided at the intermediate signal locations II and IV is all arranged substantially as described hereinbefore and eachgroupof apparatus will func tion substantially as has beendescribed in detail. The decoding .apparatusat the-headblock signal locations I and V is characterized by the omission of the directional stick relays SR and hence such apparatus is not governed by such stick relays. Specifically, control relays H and D at such locations are, controlled over circuits which correspond to the. circuits previously traced for the corresponding relays 3H and 31) at location II, with the exceptionthat at the headblock locations the control circuits do not include, the back contact 4301' the directional stick relay SR such as is employed in the control of the relays-3H and 3D at location II. f a

As stated hereinbefore, in the normal condition of the apparatus such asis illustrated in the drawings, the two track circuits of each section are supplied with three pulse clear track circuit code, with the result that the three control relays 'IP, H and D of each section are picked up and each associated signal S is caused to display its clear aspect. These track circuits are arranged to cooperate with the usual directional control means to provide an A. P. B. signal systemlwhich functions in the following manner. r

In describing the operation of the signal system embodying my invention, I shall assume that with the apparatus in its normal ccnditionas illustrated in the drawings, an eastbound train enters the first section (not shown) to the east of the first siding (also not shown) to the west of siding W represented in Fig. -la.- When thishappens, th code pattern available in the track circuit as sociated with relay I TB is shifted from the clear (three pulse) to the caution (two pulse) code,-in a manner to be made clear hereinafter and sub stantially corresponding to the manner in which code energy applied at location V to the section extending to the east thereof is shifted from the three pulse to the two pulse pattern when the eastbound train enters section I-II. With relay lTR responding to two pulse code-,relay 4D at loctaion I releases and signal IS istherefore caused to display its caution aspect. "In addition, relays ZPS and EQ associated with relay. 2TB have their respective control circuitsopened at front contact 65 of relay lD, with the result'that' the coded energy supplied from battery 2TB to the rails of section III is shifted at this time from the clear (three pulse) to the-caution (two pulse) pattern. Relay 3D at location II thereu'ponl'releases and signal (is is causedto displayits yellow or caution aspect.

This condition'of the apparatus is maintained until the train enters the section (not shown) immediately in the rear or to the west of siding W, and it provides the usual overlap protection found in A. P. B. systems. When the train enters the section in the'rear of the section with Which-relay ITR is associated, the track circuit code available for relay TR is shifted from the caution (two pulse) to the detector (one pulse) pattern, in a manner corresponding to that hereinafter pointed out whereby the code patternof energy supplied at location V to the section extending to the east of that location is similarly shifted when the eastbound train enters section IV -V.. Relay IH at location I accordingly releases and signal IS is caused to. display its redaspect. This condition obtains until the train enters the section with which relay ITR is associated, whereupon relay ITR is shunted and becomes inactive and relay ITP is caused to release.

When the train enters section I II, both relays 2TB and 3TB, are shunted and become inactive. Control relays ZTP, 2H and 2D associated with relay 2TB accordingly release and caus e signal'ZS to display its stop aspectiwhile control relays 3H and 3T3? associated with relay BTR'likewise are released and cause the associated'signal SE to display its stop aspect. In addition, 'the energizing circuits of relays 4P8 and 4Q are held-open at front contact 6| of relay 3H; while the ener gizing circuits of relays ANS and AP are held open at front contact I of relaySH. With these relays incapable of being energized, the track'circuit code supplied at location II to sec'ti on -I I III"is shifted from the clear (three pulse) .to the detector (one pulse) pattern, and this code is repeated from section II-III.into sectionlII-IV. by the cut section apparatus atlocationlll, with the result that relay 'ITR at location IV follows the detector code and relays 1H and 1D associated therewith become released, thereby causing signal TS to display its stop aspect; With relays II-Land lD released, the energizing circuit of relays 8P, 8N8, 8Q and BPS are held open and the track circuit code that is supplied at location IV to the rails of section IV-V accordingly is shifted from the three pulse (clear) pattern to the one pulse (detector) pattern, to cause relay 9TB to operate in response thereto and in turn cause relays 9H and 9D to release and cause signal 93 to display its stop aspect. Front contact 6! of relay SH is now open and it interrupt the energizing circuit of relays IGPS and HlQ,whereupon the track circuit code supplied at location V to the section that has its eastbound entrance .end at this location, is shifted fromthe clear (three pulse) to the caution (two pulse) pattern. This caution code energy will be effective to set the westbound signal at the opposite end of passing siding E to caution, thus providing that signal with the form of overlap control that corresponds to that previously described for the control of westbound signal IS at passing siding W.

From the foregoing, it is apparent that when an eastbound train enters the first section intermediate two successive passing sidings, all of the opposing signals up to the next passing siding are set to stop, while the opposing signal at the opposite end of the next passing siding is placed at caution. In addition, the westbound signal in the rear of the last mentioned signal will also be placed at caution, in a mannercorresponding to that hereinbefore described whereby signal 38 iscaused to display caution when signal IS is first shiftedto display its caution indication.

At this-time, relay 2H holds open its front contact 6! to open at that point the energizing circuits of relays IPS and IQ, while relay ZTP holds open its front contact 68 to open the energizing circuits of relays INS and I P. With relays [P and IQ held deenergized, the track circuit apparatus at location ,I that supplies track circuit energy to the section that extends to the west of that location is therefore conditioned to supply energy of the one pulse (detector) code pattern to the track rails, and will do so after the sec tion becomes vacant and relay ITR initially responds to an initiating code impulse. This initiating impulse is supplied in a manner substantially corresponding to that hereinafter explained in detail in connection with the code initiating apparatus of section I-II. The supply of the one pulse detector code ,to the rails of the section associated with relay ITR wil1 causeoperation of the decoding means at the opposite section end and, in a manner to be made clear presently, will cause the code generating apparatus at suchopposite sectionend to transmitthree pulse clear track circuit code to relay ITR, whereupon relays ID, IH and .ITP will pick up and'cause signal IS to display its clear aspect.

The previously mentioned code initiating apparatus of section III is now active to apply single pulses of code initiating or restoring energy to the rails of the associated section. This apparatus comprises a relay ZFC which is energized over a circuit extending from terminal B through back contact 66 of relay 21?, the winding of relay EEG and back contact 61 of relay 23C to terminal C. When relay ZFC picks up, its front contact 70 closes to energize relay 230 over an obvious circuit, and when relay 2B0 picks up its back contact 61 opens to deenergize relay 2FC while its front contact H closes to complete an obvious circuit for relay 2GP whereupon thatrelay is caused to pick up and close its front contact [5. When this happens, battery 2TB is connected to the track rails in series with the winding of relay 2TB, thereby applying to such rails an energizing impulse that is maintained until relay ZBC releases due to the release of relay ZFC. When relay 2B0 releases, its backcontact 6 1 closes ,to again complete the energizing circuit for relay 2FC whereupon that relay picks up and again closes its front contact to energize relay 213C. This cycle of operation is repeated as long as back contact 66 of relay Z'ITP is closed, and itis effective to cause relay 230 to intermittently pick up and release and thereby energize relay 2GP to cause that relay in turn to recurrently impress battery 2TB across the track rails. Relays 2FC and 230 are provided with slow acting characteristics selected so as to provide relatively long intervals between successive pick-up intervals of relay 23C, whereby there are impressed at this time upon the track rails successive pulses of energy that are separated from each other by relatively long intervals during which no energy is present in the track rails.v At this time, of course, this energy impressed uponthe track rails is shunted away from relay 3TH by the train and such energy has no function.

When the train enters section II--III, both re- -lays 4TB. and 5TB are shunted and become inactive. Relays 4TP, 4H, and 4D associated with relay 4TB accordingly release, and signal 48 is caused to display its stop aspect. Relay 4H is made slightly slower to release than relay 4'I'P, hence directional stick relay 48R becomes picked up over a circuit extending from terminal B through back contact of relay 38R, back con tact 16 of relay 3H, back contact 1'! of relay 3TP, back contact 18 of relay GTP, front contact 19 of relay 4H and the winding of relay 48R to terminal C. After relay 48R picks up and closes its front contact 80, a stick circuit is then completed which extends from terminal B through back contact 15 of relay SSR, back contact 82'of relay 4TP in multiple with back contact '8l. of relay 4H, and front contact 80 and the winding of relay 48R to terminal 0.

With relay 5TB, at location III released, energy from section II-III is not, of course; repeated or cascaded into section III-JV, and relay ITR. accordingly becomes inactive to cause relay 'ITP also to release.

When the train clears section III, the coded energy that is intermittently impressed on the rails of this section at location I by the associated code initiating apparatus is transmitted through the track rails and the first pulse thereof is effective to pick up relay 3TR, which relay in turn picks up the associated stick relay 3T8. At the end of the first code initiating impulse received by 'relay 3'IR, that relay releases to complete the energizing circuit of relay 3N. The code initiat ing apparatus at location I is arranged "to apply a code to the track rails comprising on intervals of energy separated from each other by oif intervals longer than the full pick-up interval of relay 3N, hence that relay will pick up prior to the time that the code initiating mean at location I supplies the succeeding code impulse. When relay 3N picks up, it will of course: start the transmission of code energy from battery 3TB to the rails. of section 1-11 at location II. At this time, stick relay 48R is picked, up but relay 4H is; released, hence relays 3NS and 3P may be energized over, back icontact 5| of relay 4H and frontcontact 52. of. relay 4SR) but relays 3PS and? 36) cannot be energized. It follows, therefore, that thecode-energy. applied at location II .to'the rails of section I- -II is of the caution (two pulse) :pattern and this energy when receivedby relay 2TB causes operation of that relay, which in turn causes relays ZTP and 2H to pick up.

The energization of the code initiating apparatus of section I.II. is terminated when, relay. ZTP opens its backcontactfifi, while signal 28 is caused to display its caution aspect. In addition, when relay 2TP picks; up, it conditionsthe energizing circuit of relays :lNS and IP to be completed, while when relay 2H picks up it conditions the energizing circuits of relays IPS and IQ to be completed, whereupon the code transmitting apparatus associated with relay ITR is rendered effectiveto transmit clear (three pulse) coded energy to the ,associatedsection. t. The operation of relay ZTR by the coded energy available in section I,II causes the code generating means associated therewith to, operate to apply coded, energy. to the rails of the. section. This code generating apparatus is conditioned to apply three. pulse (clear) track circuit code to thetrack rails, since. at this time relay ID is picked up and all of the impulse relays 2N, 2P

and 2Q are conditionedtosbe energized. This three pulse code energy is transmitted through thewrailsof section I.II where it causes operation of-relay 3TB, butat thistime only relay3TP but not relays 3H and 3D may be picked up. Relays 3H and, 3B are held releasedeven though their associated track relay responds to three pulse code energy, due to the fact that directional stick, relay 4SR is picked up and holds open the energizing circuitsof relays 3H.and 3D, at its back contact 43. The directionalstick relay 48R thus functions to retain the opposing signal 33 at stop inthe rear oflthe, train, as is the usual practicein A. P. .B. signaling. When the, train vacates section 11-111, relay 5TB, responds. to the. code initiating pulses of energy that are. appliedatlocation II to section II-III, and this relay junctions to repeat the code, initiating pulses of energy into section III-JV, but with the train in that section, these impulses are-shunted away-from relay ITRiand have no useful function at this time.

When .the train, enters section IV'V, relays 8TB. and 9TB are shunted and become inactive. Relays; 8TP, 8H and 8D associated with relay 8T,R. accordingly release to cause signal 83 to display its stop aspect, and relay BSR is caused to pick up. over a. pick-up circuit which substantially corresponds to the pick-up circuit hereinbefore traced for relay 48R at location 11. .The code initiating apparatus at location IV is now active and applies to the rails of the section single pulses of code energy that are shunted away fromurelay 9TB. .by the train. c w

l .Thecode energy applied at location V to the section that has its eastbound entrance end at this location is now shifted from the caution (two pulse) to the detector ,(one pulse) pattern, since with relay 9TB shuntedand inactive, relays 9]), 9H and .9'I'P associated therewith are released and front contact 68 .of relay STP. holds open the energizingzcircuit of relays IONS and "JP, there! by causing the code transmitting apparatus associated with relay :1 UTR. to supply single pulse code to the rails-of the associated section. This code energy is of course effective to place at stop the westbound signal at the opposite end (not shown) of passing siding E, thereby providing a controlfor that signal corresponding to the control hereinbefore described whereby signal IS is caused to assume its stop position when the train enters the section to the west of passing siding W.

When the train vacates section IIIIV, the codeinitiating pulses ofenergy applied at location II .to section 11-111 and repeated by relay GT-Rinto section III-JV,- thereupon :become effective to operate relay ITR. When this relay picks up on the first-of such pulses, relay ITS is picked up, and then when relay -'ITR release at the end of the first impulse,relay 1N.picks up to condition the code transmitting apparatus associated with relay 'lTR to supply coded energy to the rails of section IIIIV. As-stick relay BSR is now picked up, relays INS and IQ may be energized even though relay-8H is released, hence the code initiating apparatus associated with relay lTR functions to supply caution or two pulse pattern code energy to section TIL-IV. This code energy is repeated by relay 'GTR into. section 11-111 where it causes operation of relay AT-R and energization of relays 4'I'P and 4H. The following operations willnow take place: signal 48 is caused to display its caution aspect; operation of the code initiating apparatus, comprising relays AFC and 4130, is terminated when backcontact 66 of relay 4T]? picks up; relay 48B is released since its stick circuit is nowopen at the multiple-connected back contacts BI and 82 of relays 4H and 4TP, respectively; relays 3H and 3D are picked up since their respective energizing circuits are completed at back contact 43 of relay ASR; signal 3S is caused to-display its clear aspect; and the energizing circuits of all of the relays incorporated into the code transmitting apparatus associated with relay 3TB, are conditioned tobe completed with the result that such apparatus is effective to transmit clear (three pulse) code energy to section III. This-energy causes operation of relay 2TB. rand eifects the energization of relay 2B which with the previously energized rela'ys 2H and 2TP causes signal 28 to display its proceed aspect.

With relay 4TB. responding to coded energy available in the section rails, and relay 3H picked up toclose its front contacts 5| and SI, all of the impulse relays AN, '4? and lQ-are conditioned to be energized and as a result the code generating means associated with relay 4TB. operates to apply three pulse clear code energy to the track rails. This energy is repeated by relay ST-R-into section IIIIV where it causes operation'of relay 'ITR, but with relay 88R picked up to held open its back contact 45, :both relays 1H and :ID are released and signal 1S accordingly is held at stop.

When the section in advance of section IV-V is entered by the train, relay I DTR is shunted and relay IUTP, NIH and HID release to set signal IOS to stop. Then, after "the train yacates section IV-V, relay 9TB responds to the code initiating pulse of energy available in the section, and relays STS and 9N are sequentially picked up to condition the code transmitting apparatus associated therewith to transmit coded energy to section IV-V. The energizing circuits of relal BPS and 9Q are now open at front-contact .65 of relay IBD and the code transmitting apparatus associated with :rel'ay SITR zaccordingly is conditioned to transmit the "two pulse Zcaution code to the rails of section IV-V, whereupon relay 'BT-R responds to such code to pick up relays 8'I'P and 8H. Signal 8S accordingly is caused to display its caution indication; stickrelay SSR releases; relays 7H and ID pick up; and signal Isis caused to display its clear aspect. The code generating apparatus associated with relay iTR is now conditioned to transmit to the rails of the associated section III-IV three pulse code energy, which energy is repeated by relay 'GTR into section II-III where it causes response of relay 4TB and the resultant energization of relay 4D. Signal 48 accordingly is caused to display its clear aspect;

The code generating apparatus associated with relay BTR is now conditioned to transmit three pulse clear code energy to the track rails, and relay 9TB operates in response thereto and picks up relay 9D to cause signal 93 to display its clear aspect.

The initiating code energy applied at location V to thesection which has its eastbound entrance end at that location is effective when that section becomes vacant to cause the code transmittin apparatus (not shown) at the'opposite end of the section to transmit'detector code to the section in a manner which will be clear from the previous description presented in connection with the application of detector code to the section with which relay ITR is associated. This detector code is received by relay IUTR. and causes this relay to operate in such a manner as to pick up relay HJTP, thereby 'deenergizing the code initiating apparatus associated with relay IGTP. The code generating apparatus associated with relay -HJTR is now conditioned to transmit the three pulse clear code energy to the rails of the associated section and these impulses will of course maintain operation of the code transmitting apparatusat the opposite section end.

When the train clears the next adjoining section, the coded current'that is applied to the section which begins at location V is then shifted from the one pulse (detector) -pattern to the three pulse (proceed) pattern and relay IOTR accordingly operates to pick up the associated relays NH and I'OD to cause signal IDS to go to clear. In addition, when relay IOD picks up it closesgits front contact to. condition the energizing circuits of relays SP8 and 9Q to be completed, whereupon the coded current that is supplied at location V to section IV-V is then shifted from the two pulse to the three pulse pattern. Relay 8TB follows this three pulse code pattern and causes relay 8D to pick up and cause signal 8S to display its proceed indication. The apparatus represented in the drawings accordingly is restored to its normal condition wherein clear (three pulse) coded current is applied to each of the two track circuits of each section.

From the foregoing description, it is readily apparent that the apparatus embodying my invention is arranged in such a manner that when an eastbound train operates between passing sidings, that train is provided with absolute protection against opposing train movements while permissive protection is afiorded for following train movements. It is also apparent that such protection is provided without the use of line wires by means of track circuits,'two for each section and each supplied with coded energy that is generated in response to the=presence of codedenergy in the other track circuit of the .section. In addition, it is apparent that while :my invention hasbeendescribedin connectionwith an A. P. 'B.

system wherein the signals are arranged to vprovide definite limits of control-adjusted to a particular track layout, the system is inherently flexible and maybe. arranged to provide a wide variety of control limits leach adjusted to the particulartrack layout that exists at the point of application.iu.,v a i I a. i

It is believed. that the operation of the 'appa ratus embodying my invention for awestbound train movement will be readily apparent from an inspection of i the drawings taken with the foregoing descriptionof the operation foran eastbound train, and further detailed explanation of theapparatus is deemediunnecessary. i

Although I have described my invention as appliedtoa. signal system of the A. P. B. type, it will, be apparent that my invention is not limited to such systems but is;broadly useful in other single track, two direction systems, whether controlled manually from a remote location, or

automatically by the approach of ,a train.

Althoughll have herein shown anddeScrlbe-d only one formqof railway trafiic controlling apparatus embodyingmy invention, it is understood that various, changes andarnodifications may be madetherein within the scope of the appended claims without departing i'rom'the. spirit and.

scope of my invention. V i l Having thus described my invention,- what I claimis; m i f I 1. In combination, a section of railway track, two track relays of the biased. polar neutral type, one foreach end of said section, two sources of energy one for-each track relay, means controlledby one of said track relays for connecting a the windings of both of said track relays in-a trackcircuit including the rails of said section andthe source associated with said one track relay poled to' supply current having a polarity effective to pick up the other but not the said one track relay, and means controlled by the said other track relay, for connecting the windings of both of saidtrack relays in another track circuit includingsaid section rails and the other of said sourcespoled tosupply-current having a polarity effective to pick up thesaid one but not the said othertrackrelay. i a l 2. In combination, a section of railway track, means for intermittentlyiapplying afirst source of, current across the rails at one end of said section, a track relay responsive to current of a given relative polarity only,sa repeating relay, a circuit including a back contact of 'said'repeating relay for connecting the winding of said track relay across the said track rails at the'opposite end of said section forderiving therefrom current of said given relative polarity, a second source of current, another circuit including a front contact of said repeating relay. for connecting said second source in series with the winding of said track relay across the rails at said opposite section end with said second source poled to supply energy having a polarity. opposite to said given relative polarity, atrack stick relay, an impulse relay, a

pick-up circuit for said track stick relay including a front. contact of said track relay, a stick circuit forsaiditrack stick relay including its own front contact and a back contact of said impulse relay, an energizingcircuit for said impulse relay including afrontcontact of said track-stick relay and a backicontact of said track relay, an energizing circuit, for said repeating relay including atfrontcontact of said impulse relay, and means controlled byenergy of said opposite 1 relative polarity supplied from said second source to said track rails forcontrolling the intermittent application of energy from said first source to said track rails. i

3. In combination, a section of railway track, a track relayresponsive only to current of a given relative polarity and, connected to the rails at one end of said section, a code repeating relay, a source of current a circuitincluding a front contact of saidlcodarepeating relay for connecting said source to, said rails at said one section end with said source poled, to supply rail current which is of the opposite relative polarity with respect to said track relay, a stick relay, a pickup circuit for said stick relay including a front contact of said track relay, an impulse relay, a stick circuit for saidstick relay including a front contact of said stick relay and a back contact of said impulse relay, an energizin circuit for said impulse relay including a front contact of said stick relay and a, back contact of said track relay, an energizing, circuit for said repeating relay including a from contact of said impulseree lay, and means; governed by said rail current for impressin vlotherrail currentat the opposite end of said section having said given relative polarity with respect to said track relay.

4. In combination, a section of railway track,

atrack'relay responsive only to current of a given relative polarity and; connected to the rails at one end of said section, a stick relay, a pick-up circuit forsaid' stick relay including a front contact of saidtrack relay, an impulse relay, a stick circuit forsaidstick relayincluding its own front contact and a back contact of said impulse relay, an energizing, circuit for, said impulse relay in cluding a back contact of saidtrack relay and a front contact of said .stick relay, a source of C'lll'a rent, meanscontrolled ,by', said impulse relay when. picked up for connecting said source to the rails at said one section] end with said source poled to supply rail current having the opposite relative polarity with respect to said track relay, and means governed by said rail current for sup plying other rail currentat the opposite end of said section having said given relative polarity with respect to said track relay;

5. In connection, a stretch of railway track including a track circuit section, a track relay receiving energyfrom the rails atone end of said section and responsive cnly to current of a iven relative polarity, a fi rst, stick relay having a pickup circuit including a front contact of said track relay, a first slow pick-up impulserelay, a stick circuit for said first stick relay including its own front contact and a back contact of said first impulse relay, an energizing circuit for said first impulse relay includin a front contact of said firsti stick relay, a second stick relay having a pick-up circuitincluding a front contact of said first impulse relay and governed by traflic conditions on said stretch to be effective only when certain conditions exist, a second slow pick-up impulse relay, a stick circuit for said second stick relay including its own front contact and a back contact of said second impulse relay, an energize ing circuit for said second impulse relay includinga, front contact ofsaid second stick relay, a third stick relay having a pick-up circuit including afront contact of said second impulse relay and governed bytraiiic conditions on said stretch to be effective only when given conditions exist, a third slow pickup impulse relay, a stick circuit for said third stick relay including its own front contact and a back contact of said third impulse relay, "an energizingicircuit for said third impulse relay including a front-contact of said third stick relay, a source of current, means controlled by each of said impulse relays for connecting said source to the rails at said one section end with said source poled to apply energy thereto having. a polarity opposite to said: given pol'arity, and means at the opposite section end selectively responsive to said opposite polarity current for governing traffic in said section and for supplying rail current having said given relative polarity with respect to said track relay. 7

6. In a railway signal system of the A. P. B. class wherein a stretch ofrailway track is divided into a plurality of successive adjoining track sections each provided with twotrack circuits one for each direction of train movement in such section, the combination of means for applying to each of the track circuits of'each of said sectionstrack circuit energy that is codedat one or another of a plurality of different manners in accordance withtraiiic conditions on said stretch in advance for the direction of the associated" track circuit and which energy is generated in' each of the two circuits of asection' inresponse to the presence of coded energy in the other circuit of the associatedsection, and means controlled bysaid track circuits, effective upona train entering said stretch and shunting the rails of the first section thereot for controlling the generation of the coded energy applied to each of the track circuits associated with thedirection opposite to that of' the train movement to supply such circuits with energy codedin a manner indicative of the approach of a train.

'7. In'combination with a stretch of railway track divided into a plurality of successive adjoining track sections, a first directiontrack circuit for each of said sections comprising a first generating means at the sections g-i-ven endefiective at times for applying to the section rails energy impulses in groups having one or another of a plurality of difierent number of impulses in each group and a first means receiving energy from the rails at the opposite endof the sectionand including a first decoding means selectively responsive to the number of impulses in the groups there received, means controlled by the first decoding means of eachsection for. reflect lng traffic conditions in the opposite-to-given ,direction' by selecting the number of' impulses inthe groups comprising the track circuit energy applied to the said given end of the section next adjacent to that sections said opposite end", means controlled by the first decoding means of each section in accordance with the number of impulses in the groups received by such means for governing traffic in the associated section moving in said Opposite to given direction, a second direction track circuit for each section comprising a second generating means at the sections said opposite end rendered efiective by that se'ctions said energy receiving means followingthe receipt of the last impulse of each group there received for applying to the section rails energy impulses in groups having one or another of a plurality of different number of impulses in each group and a second means receiving energy from the rails at'the section's said given end and including a second decoding means selectively responsive to the number of impulsesinthe groups" there received, means controlled by the second decoding means of eachsection' for reflecting traflic conditions inthe given-to-opposite direction by selecting the number of impulses in the groups comprising the track circuit energy applied to tions first generating means following the receipt of the last impulse of each group there received.

8. In combination with a; stretch of railway track divided into a plurality of successive adjoining track sections, a first direction track circuit for each of said sections comprising a first generating. means at the sectionvsgivenend effective at times for applying to the section rails energy impulses in groups having one: or another or a; plurality of difiierent number of impulses in each group and a first means receiving energy from the'raiis at the" opposite end of the section and including a first decoding means selectively responsive to the number of impulses: in the groups there received, means controlled by the first decoding. means of each section for reflecting, traffic conditions in the opposite-to-given direction by selecting the number of impulses in the groups comprising the track circuit energy applied to. the said given end of the section next adjacent to that sections said opposite end, means controlled by' the first decoding means of each section in: accordance with the number of impulses in the groups received bysuch means for governing trafiic ingthe associated section movin in said opposite-,to-giverr direction, a second directiontrack. circuit for each section comprising asecond generating. means at the sections said opposite end rendered effective by that sections said energy receiving means following thereceipt of the last impulse of each. group: there received for applying to the section rails energy-impulses inrgroups' having one or another of a plurality ofdifferent number of impulses in each group and a second means" receiving energy from the rails at the section's said givenend-and including a second: decoding means selectively responsive to the number of impulses. in; the groups there received, means controlled by the second decoding means of each section for reflecting trafiic conditions in the given-to-opposite direction by selecting the number of impulses in the groups comprising the track circuit energy applied to the said opposite end' of. the section next adiacent tothe sectio'ns saidgiven end, means controlled by the. second decoding means of each section in accordance with the number of impulses in the groups received by such means for governing traffic in the associated section moving in said given-to-opposite direction, other means controlled by the said second energy receiving means ofeach section for rendering effective that sectionsfirst generating means following the receipt of the last impulse of each group there received, and code initiating means associated with one of the two track" circuits of each section effective when both of such circuits are shunted by a train in such section for applying to the section rails code initiating impulses which are effective after said sectionbecomesvacant to actuate the energy receiving means of such one track circuit, whereby to-restore both of such circuits-to their respective normal condition wherein the code ener y applied to each circuit is generated in response to the. receipt ofcode energy from the" other of such circuits.

9; In combination with a stretch of railway joining track sections, a first direction track cir-' cuit for each of said sections comprising a first generatingmeans at the sections given end effective at times for applying to the section rails energy impulses in groups having one or another of a plurality of difierent number of impulses in each group and a first mean receiving energy from th rails at the opposite end of the section and including a first decoding means selectively responsive to the number of impulses in the groups there received, means controlled by the first decoding means of each section for reflecting traffic conditions in the op-posite-to-given direction by selecting the number of impulses in the groups comprising the track circuit energy applied to the said given end of the section next adjacent to that sections said opposite end, means controlled by the first decoding means of each section in accordance with the number of impulses in the groups received by such means for governing trafiic in the associated section moving in said opposite-to-given direction, a second direction track circuit for each section comprising a second generating means at the sections said opposite end rendered eiTective by that sections said energy receiving means following the receipt of the last impulse of each group there received for applying to the section rails energy impulses in groups having one or another of a plurality of different number of impulses in each group and a second means receiving energy from the rails at the sections said given end and includin a second decoding means selectively responsive to the number of impulses in the groups there received, means controlled by the second decoding means of each section for reflecting tramc conditions in the given-toopposite direction by selecting the number of impulses in the groups comprising the track circuit energy applied to the said opposite end of the section next adjacent to that sections said given end, means controlled by the second decoding means of each section in accordance with the number of impulses in the groups received by such means for governing traflic in the associated section moving in said given-to-opposite direction, other means controlled by the said second energy receiving means of each section for rendering effective that sections first generating means following the receipt of the last impulse of each group there received, and means controlled by said track circuits and effective when a train enters said stretch and shunts the rails of the first-encountered one of said sections for selecting the number of impulses of the groups supplied to each of the track circuits associated with the direction opposite to that of the train movement to cause the associated trafiic governing means to prevent traffic movements in such opposite direction.

10. In combination with a stretch of railway track divided into a plurality of successive adjoining track sections, a first direction track circuit for each of said sections comprising a first generating means at the sections given end effective at times for applying to the section rails energy impulses in groups having one or another of a plurality of difierent number of impulses in each group and a first means receiving energy from the rails at the opposite end of the section and including a first decoding means selectively responsive to the number of impulses in the groups there received, means controlled by the first decoding means of each section for reflecting traflfic conditions in the oppcsite-to-given direction by selecting the number of impulses in the groups comprising the track circuit energy applied to the said given end of the sectionnext adjacent to that sections said opp site end, means controlled by the first decoding means of each section in accordance with the number of impulses in the groups received by such means for governing traffic in the associated section moving in said opposite-to-given direction, a second direction track circuit for each section comprising a second generating means at the sections said opposite end rendered effective by that sections said energy receiving means following the receipt of the last impulse of each group there received for applying to the section rails energy impulses in groups having one or another of a plurality of diiferent number of impulses in each group and a'second means receiving energy from the rails at the sections said given end and including a second decoding means selectively responsive to the number of impulses in the groups there received, means controlled by the second decoding means of each section for reflecting traffic conditions in the given-to-opposite direction by selecting the number of impulses in the groups comprising the track circuit energy applied to the said opposite end of the section next adjacent to that sections said given end, means controlled by the second decoding means of each section in accordance with the number of impulses in the groups received by such means for governingtrafiic-in the associated section moving in said given to opposite direction, other means controlled by the said second energy receiving means of each section for rendering effective that sections first generating means following the receipt of the last impulse of each group there received, code initiating means associated with one of the two track circuits of each section eiiective when both of such circuits are shunted by a train in such section for applying to the section rails code initiating impulses which are eifective after said section becomes vacant to actuate the energy receiving means of such one track circuit, whereby to restore both of such circuits to their respective normal conditions wherein the code energy applied to each circuit is generated in response to the receipt of code energy from the other of such circuits, and means controlled by said track circuits and effective when a train enters said stretch and shunts the rails of the first-encountered one of said sections for selecting the number of impulses of the groups supplied to each of the track circuits associated with the direction opposite to that of the train movement to cause the associated traffic governing means to prevent trafiic movements in such opposite direction.

11. In a coded track circuit signaling system for railroads, the combination with a track section, of means at each end of said section comprising a source of current, a code following track relay, a transmitter relay eflective when energized for impressing energy from the associated source across the track rails of said section and when deenergized for connecting the associated track relay to receive energy over the track rails of said section from the opposite end, a timing relay having a first and a second position and controlled by the associated track relay to operate from its first to its second position when said track relay remains released for an interval equal to the timing interval of said timing relay, and means rendered effective upon opeljablOn'Of said timing-relayto its saidsecondposi tion ior supplyingthe associated transmitting re la with a plurality of energy impulses with the impulses separated from each other by an interval shorter induration than the timing interval of said timing relay. u 2. In a coded track circuit signaling system for a stretch of railway track including a track section, the combination with said track section, of means at each end of said section comprising a source of current; a code following track relay, a transmitter'relay'effective when energized for impressing energy 'from the associated source across the track rails" of said section and when deenergized for connecting the associated track relay to receive energy over the track rails of said section from the opposite end, a timing relay having a first and a second position and controlled by'the associated track relay to operate from its first to its second position when said track relay remains released for an interval equal to the timing interval-oi saidtiming relay, means rendered effective upon operation of said timing relay to its'said second position for supplying the associated transmitting relay with agroup of energy impulses having one or another of a plu rality offdifferent number of impulses with the impulses-in the group separated from each other by an interval shorter in duration thanthe timing interval of said timing relay, and means controlled :by trafiie in said stretch beyond the associatedendiof the-section for. selecting the'number of impulsesinthe' groupsupplied by said last mentioned means to said transmitting relay.

13. In a coded track circuit signaling system for a stretch of railway track including a track section, the combination with said track section, of means at each'end of said section comprising a source of current, a code following track relay,

a transmitter relay effective when energized for impressing energy from the associated source across the track rails of said section and when deenergized for connecting the associated track relay ,to'receive energy over the track rails of said section from the opposite end, a timing relay having a'first and a second position and controlled by the associated track relay to operate from its first to its second position when said track relay remains released for an interval equal to the timing interval of said timing relay, means rendered effective upon operation of said timing relay to its said second position for supplying the associated transmitting relay with a group of energy impulses having one or another ofa plurality of different number of impulses Wi h the impulses in the group separated from ea 11 other by an interval shorter in duration than tl e timing interval of said timing relay, means controlled by trafiic in said stretch beyond the'associated end of the section for selecting the number of impulses in the group supplied by said last mentioned means to said transmitting relay, and decoding means operated by the associated track relay and selectively responsive to the number of impulses in the group operating the associated track relay.

' HOWARD A. THOMPSON. 

